METHOD OF OPERATING A MICROLITHOGRAPHIC PROJECTION APPARATUS AND ILLUMINATION SYSTEM OF SUCH AN APPARATUS

• US 20180217506A1
• Filed: 02/20/2018
• Published: 08/02/2018
• Est. Priority Date: 09/23/2015
• Status: Active Grant

• Current Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Inventors: Deguenther, Markus, Eisenmenger, Johannes, Hilt, Stefanie, Korb, Thomas, Schlesener, Frank, Maul, Manfred
• Granted Patent: US 10,444,631 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 3/0062 Stacked lens arrays, i.e. refractive surfaces arranged in at least two planes, without structurally separate optical elements in-between
• CPC Class Codes: G03F 7/70075 Homogenization of illumination intensity in the mask plane by using an integrator, e.g. fly's eye lens, facet mirror or glass rod, by using a diffusing optical element or by beam deflection
• CPC Class Codes: G03F 7/70116 Off-axis setting using a programmable means, e.g. liquid crystal display [LCD], digital micromirror device [DMD] or pupil facets
• CPC Class Codes: G03F 7/702 Reflective illumination, i.e. reflective optical elements other than folding mirrors, e.g. extreme ultraviolet [EUV] illumination systems
• CPC Class Codes: G03F 7/7085 Detection arrangement, e.g. detectors of apparatus alignment possibly mounted on wafers, exposure dose, photo-cleaning flux, stray light, thermal load

Abstract

An illumination system of a microlithographic projection apparatus includes a spatial light modulator having a modulation surface including a plurality of micromirrors. Each micromirror includes a mirror surface having an orientation that can be changed individually for each micromirror. For at least one of the micromirrors, at least one parameter that is related to the mirror surface is measured. The orientation of the mirror surfaces is controlled depending on the at least one measured parameter. A light pattern is produced on the modulation surface, and an image of the light pattern is formed on an optical integrator that has a plurality of light entrance facets. Images of the light entrance facets are superimposed on a mask.

Claims

1. A method of operating an illumination system of a microlithographic projection apparatus, the illumination system comprising a spatial light modulator comprising a modulation surface comprising a plurality of micromirrors, each micromirror comprising a mirror surface having an individually changeable orientation, the method comprising:

for at least one of the micromirrors, measuring a parameter related to the mirror surface to provide a measured parameter;

controlling the orientation of the mirror surface depending on the measured parameter;

producing a light pattern on the modulation surface;

forming an image of the light pattern on an optical integrator comprising a plurality of light entrance facets; and

superimposing images of the light entrance facets on a mask.

2. The method of claim 1, wherein the measured parameter is selected from the group consisting of a position of the mirror surface and an orientation of the mirror surface.

3. The method of claim 1, wherein measuring the parameter comprises measuring an angular irradiance distribution at least at one field point in a mask plane or a plane that is optically conjugate to the mask plane.

4. The method of claim 3, wherein the measured parameter comprises the orientation of the mirror surface, and the method comprises measuring the angular irradiance distribution at a plurality of field points in the mask plane or a plane that is optically conjugate to the mask plane.

5. The method of claim 4, comprising simultaneously measuring the angular irradiance distribution at the plurality of field points.

6. The method of claim 5, wherein the illumination system comprises a plurality of position resolving light sensors arranged at positions that are associated with the plurality of field points, and the method comprises using each light sensor to measure the angular irradiance distribution for the associated field point.

7. The method of claim 1, wherein measuring the parameter comprises measuring an irradiance at least at one field point in a mask plane or a plane that is optically conjugate to the mask plane.

8. The method of claim 7, wherein the measured parameter is the orientation of the mirror surface, and the method comprises measuring irradiance at a plurality of field points in the mask plane or a plane that is optically conjugate to the mask plane.

9. The method of claim 8, comprising simultaneously measuring irradiance is at the plurality of field points.

10. The method of claim 9, wherein the illumination system comprises a plurality of light sensors arranged at the plurality of field points, and the method comprises using each light sensor to measure the irradiance at the associated field point.

11. The method of claim 1, wherein measuring the parameter comprises computing the based on a shape of the mirror surfaces, a spatial arrangement of the modulation surface relative to the light entrance facets, and a shape of the light entrance facets.

12. The method of claim 1, wherein the parameter is measured while controlling the orientations of the mirror surfaces so that adjacent mirror surfaces do not superimpose light on the mask.

13. The method of claim 1, wherein the parameter is measured while detecting a position of a marker point that is fixedly arranged with respect to the spatial light modulator.

14. The method of claim 13, wherein the spatial light modulator comprises at least two modulator units, each modulator unit comprises a plurality of micromirrors, and each modulator unit supports at least one marker point.

16. The method of claim 13, wherein the marker point is imaged on a position resolving light detector that is fixedly arranged with respect to the optical integrator.

18. The method of claim 1, wherein the modulation surface is observed by a camera which detects light that has been reflected or scattered by the micromirrors or by structures between the micromirrors.

19. The method of claim 1, wherein controlling the orientation of the mirror surface comprises laterally shifting a control pattern when the mirror surface has been measured as being laterally displaced.

15. (canceled)

17. (canceled)

20. A method of operating an illumination system of a microlithographic projection apparatus comprising a spatial light modulator comprising a modulation surface comprising a plurality of micromirrors, each micromirror comprising a mirror surface having an individually changeable orientation, the method comprising:

for at least one of the micromirrors, measuring a parameter related to the mirror surface to provide a measured parameter;

controlling the orientation of the mirror surface depending on the measured parameter;

producing a light pattern on the modulation surface; and

forming an image of the light pattern on a field plane.

21. An illumination system, comprising:

a spatial light modulator comprising a modulation surface which comprises a plurality of micromirrors, each micromirror comprising a mirror surface having an individually changeable orientation;

a measuring device configured to measure, for at least one of the micromirrors, a parameter that is related to the mirror surface to provide a measured parameter;

a control unit configured to control the orientation of the micromirrors depending on the measured parameter;

an optical integrator comprising a plurality of light entrance facets; and

an imaging optical system configured to provide an image of the modulation surface on the optical integrator.

22-31. -31. (canceled)

32. An illumination system, comprising:

a spatial light modulator comprising a modulation surface comprising a plurality of micromirrors, each micro-mirror comprising a mirror surface having an individually changeable orientation;

a measuring device configured to measure, for at least one of the micromirrors, a parameter related to the mirror surface to provide a measured parameter;

a control unit configured to control the orientation of the micromirrors depending on the measured parameter; and

an imaging optical system configured to form an image of the modulation surface on a field plane.